Accurately determining and indicating the amount of fuel contained within a fuel tank can often be critical for a vehicle operator. The fuel level may be used to determine when and where the vehicle should be refueled prior to the fuel tank being emptied. A typical fuel tank utilizes a dedicated fuel level sensor, such as a floating sensor, to determine the amount of fuel remaining in the fuel tank. However, if the floating sensor becomes stuck, malfunctions, or becomes decoupled from the vehicle powertrain control module, the fuel level may become unknown. An in-dash fuel level gauge may provide an inaccurate or indeterminate fuel level to the vehicle operator. This may lead to the vehicle running out of fuel if the fuel level indicator suggests fuel is still remaining in the tank, or may lead to increased operator anxiety stemming from not knowing how much fuel is remaining in the tank.
Periodically, diagnostic tests may be performed on the fuel level indicator. However, current tests often include monitoring output of the fuel level indicator over a period of 100 miles of engine combustion. For hybrid vehicles, and other vehicles capable of operating without engine combustion for long periods of time, the test may take a long time to complete. Further, such a test does not necessarily cover the entire range of the fuel level indicator. A fuel level indicator that is prone to stick or has a worn resistive track that effects output only at certain fuel levels may go undiagnosed.
Other attempts to address fuel level indicator degradation include monitoring the output of a fuel level indicator during a refueling event. One example approach is shown by Grunwald et al. in U.S. Pat. No. 7,458,246. Therein, fuel temperature is monitored during a refueling event, and the change in fuel temperature is used to discern the change in fuel volume, which is then compared to the fuel level indicator output.
However, the inventors herein have recognized potential issues with such methods. For example, this strategy may not adequately gauge the entire range of the fuel level indicator. Additionally, such strategies may not discern between electrical and mechanical degradation of the fuel level indicator. As such, it may not be possible to predict how the fuel level indicator output may be affected during a fuel consumption cycle. Accordingly, the reported fuel level cannot be adjusted intrinsically, and thus may provide incorrect information to the vehicle operator during certain ranges of fuel level indicator output.
In one example, the issues described above may be addressed by a method for a fuel system that comprises receiving a first indication of inconsistency in a fuel level indicator output during a fuel consumption cycle, receiving a second indication of inconsistency in a fuel level indicator output during a refueling event, and indicating electrical degradation of the fuel level indicator responsive to the first and second indications of inconsistency indicating coincident ranges of inconsistency for the fuel level indicator output. By gauging the consistency of a fuel level indicator output during both upward and downward travel, electrical degradation may be distinguished from mechanical degradation. In this way, a range of inconsistency may be determined, and a reported fuel level adjusted while the fuel level indicator output is within the range of inconsistency.
As one example, the reported fuel level may be based on an inferred fuel level while the fuel level indicator output is within the range of inconsistency. An inferred fuel level may be determined based on a summation of fuel consumption following a refueling event or other time point where the fuel fill level is known independently from the fuel level indicator output. In this way, the reported fuel level can achieve a degree of accuracy for the entirety of the fuel level indicator range, despite the electrical degradation.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.